EP3107991A1 - Method for preparing organic waste - Google Patents

Abstract

The invention relates to a method for preparing organic waste, such as biomass or waste waters, for further processing, in particular for gasification. According to said method, in a first process step the organic waste is fed to an aerobic and/or anaerobic digester (1) and is mixed with an inoculum, and in a second process step the CO₂ produced in the digester (1) is fed to a gas reformer (7) in which it is converted to methane gas.

Description

 Process for the preparation of organic waste

The invention relates to a method for the preparation of organic waste, such as biomass or wastewater, for further processing, in particular for gasification or discharge into existing systems.

State of the art

The decomposition of organic substances produces gas, and to a considerable extent CO 2 and methane. An important component of this biogas is methane, which can be used as heating gas and for combustion drives as well as starting material for synthetic products, for example acetylene, synthesis gas, HCN and chlorine substitution products. Due to the importance of methane, efforts are being made to achieve a high methane content in the production of biogas. According to the state of the art, one or two-stage fermentation processes are used for this purpose, in which biogas is obtained from organic substances by means of anaerobic fermentation. However, a major component of this gas is C02, as well as smaller amounts of nitrogen, hydrogen sulfide and other components. However, these known methods are unsatisfactory in terms of the quality of the biogas produced and in particular the methane yield. In particular, the high sulfur or hydrogen sulfide content of about 2% is undesirable, since this has a disturbing effect on the operation of engines and the associated use of catalysts.

For this reason, EP 1 1 18 671 proposes a three-stage process, wherein in a first process step of the aerobic fermentation organic material is fermented under aerobic conditions by means of fermentation microorganisms, solid and / or liquid residues and C02-containing exhaust gases are formed in one second process step residues from the first process step are verschwelt, wherein a charcoal product and wood gas are formed, and in a third step of the thermophilic methane fermentation wood gas from the second process step under anaerobic conditions by means of thermophilic

Fermentation microorganisms is fermented to methane-containing biogas.

Object of the invention

The present invention is primarily based on the object of once again improving the methane gas produced, d. H. to create a biogas containing over 90% methane. Solution of the task

To solve the task leads that - In a first stage of the process, the organic waste is introduced into an aerobic and / or anaerobic fermenter and mixed with an inoculum and / or microorganism, and

in a second process stage, the CO 2 produced in the fermenter is fed to a gas reformer in which a conversion into methane gas takes place. This means that a clear separation between the aerobic and the anaerobic fermenter and the gas reformer is performed. The gas reformer is designed exclusively to take the C02 from the two fermenters and make it an improved methane gas. The aerobic fermenter inoculated with a corresponding aerobic inoculum produces by fermentation, on the one hand, the above-mentioned CO 2 and, on the other hand, a residual biomass which is discharged, pressed, pelleted and e.g. a biomass gasifier can be supplied. Still existing process water is introduced into the anaerobic fermenter and further processed there. The C02 is transferred to the gas reformer.

In the anaerobic fermenter is a corresponding anaerobic inoculum. In the anaerobic fermenter, especially the liquid biomasses are processed to CO 2 and methane, whereby ultimately the liquid wastewater is converted into process water by this processing, which can be discharged into the sewer. The resulting CO 2 and methane is then fed back to the gas reformer.

By special microbial loading on a very large surface then takes place in the gas reformer, the processing of CO 2 to a methane, with a methane of over 90% can be achieved. figure description

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing; This shows in its single figure a schematic representation of a plant for carrying out the inventive method for the preparation of organic waste for further processing.

In this case, 1 denotes an aerobic fermenter which has an inlet 2 for biomass. Preferably, the mass is introduced to a solids content of 20% in this aerobic fermenter and there inoculated with a corresponding inoculum. The mass is due to the high liquid content to a liquid, pulpy mass. The process temperature is controlled by an introduced, not shown heating coil at a constant 37 to 38 ° C. The heating coil is preferably in communication with a hot water circuit.

With the help of air or oxygen nozzles, the biomass is additionally circulated.

The rapidly degradable components of the biomass (sugars, fats, proteins) are reduced to CO 2, CO, H 2 and O 2 under air and / or O 2 feed. The gas produced during the air supply has a relatively high O 2 content and must therefore be subjected to an oxygen-simulating process.

In the upper part of the fermenter 1, a gas dome is formed in which this gas accumulates. Here is also a constant control of the collecting gas. In particular, in the application of pure oxygen, the gas, which still contains too much oxygen should be performed in a loop 3 of the gas dome 4 back to an inlet 5 at the bottom 6 of the fermenter 1. This happens until no or little 02 in the Gas dome 4 is present. Then, the gas from the gas dome 4, which essentially comprises CO 2, is transferred to a gas reformer 7.

After about one day, the residual biomass is discharged and e.g. Pressed and pelletized fed to a biomass gasifier not shown in detail. There it is mined except for the mineral components. The process water is transferred via a line 8 to an anaerobic fermenter 9 and degraded there to service water. In the aerobic fermenter 1 in addition to a temperature control and a constant pH determination to optimize the process.

In the anaerobic fermenter 9, in addition to the process water from the aerobic fermenter 1, biological waste water can also be introduced through a further inlet, not shown. It is designed in a special way to purify this wastewater. These include, in particular, wastewater from agriculture and food production, for example liquid manure, press water, waste water from slaughterhouses, glue manufacturers, etc. Initial tests have also shown that the reactor can be used to clean landfill leachate.

A microbial feed takes place after cultivation and propagation of a respective anaerobic inoculum by colonization of the carrier systems located in the reactor. In this case, in different densities, microbial settlement cords are stretched in the reactor, which offer a large-area settlement facility. These can consist of plastic cords, hemp ropes or sheets of pure carbon fabrics. Above all, the latter material has a very large surface of up to 1800 sqm / g as a carrier for the bacteria.

The liquid transport in the reactor is also via an external line 10. The liquid rises in two outer chambers 1 1 and 12 and then passed through a central tube 13 back down. This cycle is circulated until sufficient degradation and then discharged the remaining mass, pressed or pelletized. The liquid can be spent as process water in the sewage system.

The anaerobic fermenter 9 degrades liquefied biomass or water to a solids content of about 10% in a period of a maximum of 2 to 3 days. In a gas dome 14 C02 and methane accumulates, with a methane content of 60 to 82% is achieved in significant quantities. H2S is reduced to less than 0.1 ppm.

The temperature control of 55 to 56 ° C is preferably carried out by a heating coil, which is also controlled from the outside with hot water. In addition to constant temperature control, permanent pH measurements and CH4 controls are also carried out.

Gas reformer 7 is characterized by its unique ability to convert C02 to CH4 in a high temperature methanogenesis process. For this he needs above all the largest possible surface as a carrier substance for the thermophilic microbes. The microbial feed is carried out by a methanol crayfish strain and a bacterium thermoautotrophic on a special lignite industrial coke with a large surface area. Within the reformer is about 500 kg. Industrial coke. One gram of this industrial coke has a surface area of 220 square meters, so that the coke filling thus offers approximately a surface of 1 10 square km or 1 0 000 000 square meters.

In the reactor, this industrial coke is above a nutrient solution for the microbes and the water that forms in the reaction, separated by a grid. A temperature control of 75 to 78 ° C is controlled by a heating coil, which is incorporated in the gas reformer 7, from the outside by hot water. In addition to the multiple temperature control, a permanent measurement of CO 2, CO and CH 4 is carried out, as well as the PH value is controlled to control the optimal process.

At higher CO 2 levels, gas from the gas dome 15 can be recirculated until the desired CH 4 content (e.g., greater than 90% level) is reached.

This gas reformer 7 is particularly suitable for converting CO 2 exhaust gases into CH 4 to replace a CO 2 emission. This is especially important for wood gasifiers, wood and coal power plants and large engines, which receive their gas from mesophilic methanogenesis processes (low CH4 content). However, with such a gas reformer 7 all conventional sewage treatment plants or biogas plants can be retrofitted.

The methane gas with a methane content of 80 to 95% methane is supplied from an outlet 16 for further utilization.

Dres. WEISS & ARAT

 Patent attorneys and lawyer

 European Patent Attorney

Reference: P 4641 / DE-II Date: 03.02.14 W / ST

 LIST OF REFERENCE NUMBERS

 1 aerobic fermenter 34 67

2 inlet 35 68

3 loop 36 69

4 gas dome 37 70

5 inlet 38 71

6 floor 39 72

7 gas reformer 40 73

8 line 41 74

9 anaerobic fermenter 42 75

10 outside line 43 76

1 1 outer chamber 44 77

12 outer chamber 45 78

13 central tube 46 79

14 gas dom 47

 15 gas dome 48

 16 outlet 49

 17 50

 18 51

 19 52

 20 53

 21 54

 22 55

 23 56

 24 57

 25 58

 26 59

 27 60

 28 61

 29 62

 30 63

 31 64

 32 65

 33 66

Claims

claims 1. A process for the preparation of organic waste, such as biomass or wastewater, for further processing, in particular for gasification, wherein - In a first process step, the organic waste in an aerobic and / or anaerobic fermenter (1, 9) entered and with a Inoculum can be spiked and  - In a second stage of the process in the fermenter (1, 9) resulting CO 2 is fed to a gas reformer (7), in which a conversion into methane gas takes place. 2. The method according to claim 1, characterized in that the biomass in the fermenter (1) is entered as a liquid pulpy mass. 3. The method according to claim 1 or 2, characterized in that the temperature in the fermenter (1) at 37-38 "C is maintained. 4. The method according to at least one of the preceding claims, characterized in that the fermenter (1) oxygen is supplied. 5. The method according to at least one of the preceding claims, characterized in that in the fermenter (1) resulting gas is limited in terms of the oxygen content. 6. The method according to at least one of the preceding claims, characterized in that in a gas dome (4) of the fermenter (1) accumulating CO 2 is then forwarded to the gas reformer (7), if the in the gas dome (4) also present oxygen is reduced to a minimum. 7. The method according to claim 6, characterized in that the gas which accumulates in the gas dome (4) is circulated until the oxygen content is reduced to a minimum or no oxygen is present. 8. The method according to any one of the preceding claims, characterized in that the remainder biomass discharged from the fermenter (1) and further processed. 9. The method according to at least one of the preceding claims, characterized in that the conversion of the CO 2 in the gas reformer (7) in methane is done by microbial way. 10. The method according to claim 9, characterized in that a microbial loading of the gas reformer (7) by a Methanosarcinastamm and a bacterium Thermoautotrophicum takes place on a brown coal industrial coke with a large surface area. 1 1. Method according to at least one of the preceding claims, characterized in that in the gas reformer (7) a temperature at 75-78 ° C is maintained. 12. The method according to at least one of the preceding claims, characterized in that between the fermenter (1) and the gas reformer (7), an anaerobic fermenter (9) is turned on. 13. The method according to claim 1 1, characterized in that a temperature in the anaerobic fermenter (9) is maintained at 55-56 ° C. 14. The method according to claim 12 or 13, characterized in that the anaerobic fermenter (9) is charged with waste water. 15. The method according to at least one of claims 12-14, characterized in that in a gas dome (14) of the anaerobic fermenter (9) C02 and methane accumulates, which is fed to the subsequent gas reformer (7). 16. The method according to at least one of claims 12-15, characterized in that gas from the aerobic fermenter (1) in the anaerobic fermenter (9) is transferred. 17. The method according to claim 15 or 16, characterized in that in the gas dome (14) of the anaerobic fermenter (9) accumulating gas is at least partially recycled, until in the gas dome (14) only C02 and methane is present.